U.S. Pat. No. 4,393,960, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a brake shoe structure that includes a series of alternating long brake shoes and short brake shoes mountable on adjacent brake beams in a railroad car retarder. The length of the long brake shoe is such that the long brake shoe symmetrically straddles two adjacent brake beams. The length of the short brake shoe is such that the shoe occupies the spacing on the brake beams between two long brake shoes. The long brake shoes are affixable to each of the brake beams in at least two locations. The brake shoes contain a plurality of slanting slots in their braking surfaces for interrupting harmonics producing screeching noises during retardation. The brake shoes may be formed of steel or heat treatable ductile iron.
U.S. Pat. No. 7,140,698, the disclosure of which is hereby incorporated herein by reference in entirety, discloses a hydraulic control and operating system for a railroad car retarder to control the movement of railroad cars in a railroad classification yard. The system utilizes a double-acting hydraulic cylinder to operate the retarder mechanism and includes a hydraulic control circuit that provides protection against pressure spikes and high pressure excursions, high and low temperature excursions, low oil levels and oil filter fouling. The system shuts itself down to prevent damage, and provides a warning to maintenance staff that service should be performed long before a need for system shut-down is required. The system includes a central operating panel in the rail yard control center, a remote control panel located at the position of the retarder, and the system can be connected for operation from a completely remote location.
U.S. Pat. No. 8,413,770, the disclosure of which is hereby incorporated herein by reference in entirety, discloses systems for and methods of operating electro-hydraulic retarders. In one example, a system is provided for retarding the speed of a railcar. The system includes a brake, a hydraulic actuator coupled to the brake, and a hydraulic circuit that directs pressurized hydraulic fluid to the actuator. The fluid causes the actuator to move the brake towards a closed position in which the brake will apply a predetermined braking pressure on a wheel of the railcar. A hydraulic accumulator is coupled to the hydraulic circuit and configured to accumulate fluid from the hydraulic circuit when the wheel forces the brake out of the closed position and to supply pressurized accumulated fluid back to the hydraulic circuit when the brake moves back into the closed position to thereby maintain a substantially constant braking pressure on the wheel of the railcar as it moves through the brake.
U.S. Pat. No. 8,499,900, the disclosure of which is hereby incorporated herein by reference in entirety, discloses electro-hydraulic retarders designed to allow opposing brake shoes on the retarder to spread to the width of a wheel entering the retarder, and yet still maintain a desired braking pressure on the sides of the wheel. In one example, the retarder includes a brake and a brake actuator that has a piston-cylinder and a spring. One or both of the piston and the cylinder acts on the brake and the other of the piston and the cylinder acts on one end of the spring. The other end of the spring acts on the brake. In one example, the spring is wrapped around the cylinder and connected thereto in series. In such an arrangement, supplying pressurized hydraulic fluid to the piston-cylinder causes both the piston-cylinder and the spring to move the brake towards a closed position in which the brake will apply a predetermined braking pressure on a wheel of the railcar. The spring resiliently biases the brake into the closed position to maintain a substantially constant braking pressure on the wheel of the railcar as it moves through the retarder.
U.S. Patent Application Publication No. 2011/0315491, the disclosure of which is hereby incorporated herein by reference in entirety, discloses systems for retarding the speed of a railcar. In one example, a hydraulic actuator moves a brake between a closed position in which the brake applies braking pressure on a railcar wheel, and an open position in which the brake does not apply braking pressure on the railcar wheel. A pump supplies hydraulic fluid into at least one of a first manifold and a second manifold of a hydraulic circuit. A logic element reacts to maintaining a selected pressure in the first manifold when a railcar wheel enters a brake and moves the brake from the closed position to the open position to cause a selected braking pressure to be applied to the railcar wheel. A control circuit controls the logic element to apply the selected braking pressure on the railcar wheel.